docs: def unescape_single_character(match):
      """
      Unescape a single escape sequence found from a MySQL string literal,
      according to the rules defined at:
      https://dev.mysql.com/doc/refman/5.6/en/string-literals.html#character-escape-sequences
  
      :param match: Regular expression match object.
  
      :return: Unescaped version of given escape sequence.
      :rtype: str
      """
      value = match.group(0)
      assert value.startswith("\\")
      return MYSQL_STRING_ESCAPE_SEQUENCE_MAPPING.get(value) or value[1:]